The advantages of operating a refrigeration system compressor continuously for wide ranging thermal loads without cycling are set forth in my U.S. Pat. No. 4,742,689, reference to which is made for further particulars. One drawback of the system described in that system was the possibility that the refrigerant bypass valve which opened to bypass liquid phase refrigerant directly into the suction line would become stuck open with the most undesirable consequence that incompressible liquid-phase refrigerant entered the suction inlet of the compressor and led to catastrophic destruction of the compressor by a process known in the art as "slugging".
In some industrial heating and cooling applications, such as with chillers applied within plasma etching processes, the present state of the art is to provide refrigeration equipment for cooling and electrical elements for heating. There are numerous drawbacks to this hybrid approach. The first drawback is that the hybrid approach is very inefficient and wastes valuable energy. Heat generated in the refrigeration compressor is wasted, particularly in a system which uses continuous compressor operation as disclosed in the referenced U.S. Pat. No. 4,742,689. A second drawback is that industrial safety specifications increasingly require thermal protection devices to protect against overheating by the electrical heating element. It is very difficult to fit the electrical tank heaters with thermal protection devices which will work reliably to protect against thermal overload.